Transfer switch for tap-changing transformers convertible for adaptation to a wide range of currents



Dec. 26, 1967 A, SQHUNDA 3,360,618

TRANSFER SWITCH FOR TAP-CHANGING TRANSFORMERS CONVERTIBLE FOR ADAPTATION TO A WIDE RANGE OF CURRENTS Filed April 13, 1966 3 Sheets-$heet 1 INVENTOR Z 3,360,618 ERTIBLE A SCHUNDA Dec. 26, 1967 A w N A T n MD I A W m H F E F S N A R T 3 Sheets-Sheet 2 Filed April 15, 1966 T l a 3 R QZJ A. Z- .7 L 6 m R u 8 M l 2 P. I 3 v f 1 v mw l 6 1 .fl p I r .b fi 4 B M w 7 i M I 5 6 W mm D 3,360,618 MERS CONVERTIBLE CURRENTS 3 Sheets-$heet 5 Dec. 6. 1967 A. SCHUNDA TRANSFER SWITCH FOR TAP-CHANGING TRANSFOR FOR ADAPTATION TO A WIDE RANGE OF Filed April 13, 1966 m T N E V m MAMMM M 2%.

United States Patent 3,360,618 TRANSFER SWITCH FOR TAP-CHANGING TRANS- FORMERS CONVERTIBLE FOR ADAPTATION TO A WIDE RANGE OF CURRENTS Anton Scltunda, Regensburg, Germany, assignor to Maschiuenfabrik Reinhausen Gebruder Schenbeck K.G., Regensburg, Germany Filed Apr. 13, 1966, Ser. No. 542,702 Claims priority, application Germany, Apr. 15, 1965, M 64,893 6 Claims. (Cl. 200-11) This invention relates to transfer switches for tap changing regulating transformers.

It is a general object of this invention to provide improved transfer switches for tap-changing regulating transformers.

Heretofore transfer switches for tap-changing regulating transformers have been designed in two different ways, depending upon the magnitude of electric currents to be carried. If the magnitude of the currents to be carried continuously is relatively small, there is no need for providing current-carrying contacts in addition to main contacts and auxiliary contacts, which are both arcing contacts. On the other hand, if the magnitude of the currents to be carried continuously is relatively large, it is necessary, or desirable, to provide current-carrying contacts specially designed to perform current-carrying duty in addition to main contacts and auxiliary contacts which are both subjected to arcing and may be specially designed to perform that duty, and that duty only, if the particular piece of equipment is provided with currentcarrying contacts. The fact that different transfer switch structures are needed depending upon the magnitude of the currents to be switched and carried continuously results in greatly increased manufacturing cost due to the required duplication of parts.

It is, therefore, another object of this invention to provide module type transfer switches for tap-changing regulating transformers which may readily be adapted, or converted, to cover a very wide range of currents, thus drastically reducing the required number of parts and the manufacturing cost of transfer switches.

Load tap-changers include selector switches and transfer switches. The selector switches serve the purpose of selecting a particular tap on a tapped transformer winding intended to be connected into an electric circuit. The contacts of selector switches in the process of change do not carry load currents. Hence selector switches are not required to interrupt a current-carrying circuit, or to close on a current-carrying circuit. As a result, the contacts of selector switches are not subjected to arcing. The transfer switches perform all switching operations under load and their contacts are subjected to arcing, except the currentcarrying contacts thereof the provision of which, in addition to main and auxiliary arcing contacts, is optional. As is apparent from the foregoing, current-carrying must be provided only when the currents to be carried are relatively large, and if present, each pair of current-carrying contacts shunts one pair of main contacts. In a given design the current-carrying contacts may be dispensed with if the currents intended to be carried continuously are relatively limited.

It is, therefore, another object of this invention to provide transfer switches having current-carrying contacts which switches are designed in such a way that the current-carrying contacts thereof may readily be omitted from the switch structure in any instance the presence thereof is not deemed necessary.

The foregoing and other general and special objects of the invention will more clearly appear from the ensuing particular description of the invention, as illustrated in the accompanying drawings wherein FIG. 1 is a diagram of a transfer switch embodying this invention showing a transformer energizing the transfer switch, the selector switch normally included in such a circuit being deleted in FIG. 1;

FIG. 2 is a vertical section of a transfer switch embodying this invention, main current-carrying contacts being deleted from the structure;

FIG. 3 is a vertical section of a portion of the structure of FIG. 1 including main current-carrying contacts;

F IG. 4 is a section along IVIV of FIG. 3;

FIG. 5 shows a portion of the structure of FIG. 3 on a larger scale and FIG. 6 is a section along VI-VI of FIG. 5.

Referring now to the drawings, numeral 1 has been applied to indicate a cylindrical switch housing of insulating material. As seen from above fixed main contacts 2 and fixed auxiliary contacts 2 are arranged along a sector of a circle. Contacts 2 and 2 are abutting against and supported by the radially inner surface of switch housing 1. Movable main contacts 3 are provided to cooperate with fixed main contacts 2, and movable auxiliary contacts 3 are provided to cooperate with fixed auxiliary contacts 2'. Transformer winding Tr has two terminals U U The former is conductively connected to left fixed main contact 2 and left fixed current-carrying contact 25 and the latter is conductively connected to right fixed main contact 2 and right fixed current-carrying contact 25 (FIG. 1). Fixed auxiliary contacts 2' are connected by the intermediary of ohmic resistors R to taps U U of winding Tr. Each movable contact 3, 3 is supported by a contact support 30 the ends of which engage radial grooves 4a, 5a in a pair of horizontal plates 4, 5. Each movable contact 3, 3' is insulated by a layer of insulation (not shown) from the contact support 30 by which it is supported. Each contact support 30 includes a vertical operating shaft 31 whose axially outer ends rest in bearings formed by each contact support 30. Each contact support further defines a central bearing for shaft 31. The operating shaft 31 of each contact support 30 is adapted to be moved radially outwardly and radially inwardly to cause disengagement of contacts 3, 3' from contacts 2, 2, or engagement of contacts 3, 3' with contacts 2, 2'. The movement of the operating shafts 31 of the several contact supports 30 is being effected by means of pairs of linkages to which reference numeral 8 has been applied. The radially inner ends of the several linkages 8 pertaining to contact supports 30 of the movable contacts 3, 3' of one phase of the transfer switch are tied together by a vertical shaft 32. Reference numeral -11 has been applied to indicate a main shaft formed by three vertical plates or fins enclosing angles of degrees. An upper contact-operating plate 10 and a lower contactoperating plate 10 are fixedly mounted on main shaft 11 for joint pivotal motion with main shaft 11 in clockwise and counterclockwise direction. Helical springs 9 are interposed between the radially outer ends of contact-operating plates 10 and the ends of shaft 32. Pivotal motion of main shaft 11 in either clockwise or counterclockwise direction causes sequential operation of movable main contacts 3 and of movable auxiliary contacts 3.

The above referred-to lower grooved plate 5 for guiding the supports 30 for the movable contacts 3, 3' is substantially spider-shaped, i.e. it has arms 6 which extend radially outwardly and have radially outer ends engaging the radially inner surface of switch housing 1 and being secured to that surface of switch housing 1. The upper grooved plate 4 and the lower grooved plate 5 are tied together by means of vertical ribs 7. Plates 4 and 5 and ribs 7 thus form a squirrel-cage frame supporting all the movable parts of the transfer switch structure. This squirrel-cage frame structure may be at ground potential and form the neutral point of the electric system of which the transfer switch forms a part.

The spider-shaped plate or support 5 and the upper plate 4 are each provided with a roller bearing 12 for supporting main operating shaft 11. Spider-shaped support 5 further defines a central upper bore 13 of relatively small diameter and a central lower internally screw-threaded bore 14 of relatively large diameter. An externally screw-threaded hub member 19 is screwed into lower bore 14. Hub-member 19 defines jointly with spider-shaped support 5 a circular groove to which reference character 20 has been applied. Upper bore 13 in spider-shaped support 5 forms a bearing for an auxiliary shaft 15. Shaft 15 is intended to operate movable current-carrying contacts and the provision of shaft 15 is optional and only necessary if the current-carrying capacity of the transfer switch is of such a magnitude as to require the provision of current-carrying contacts in addition to the main contacts 2, 3 and the auxiliary contacts 2', 3'. Auxiliary shaft 15 may be driven by main operating shaft 11, both said shafts being arranged in coaxial relation. In order to drive auxiliary shaft 15 by means of main operating shaft 11 the juxtaposed ends of both shafts are provided with an appropriate coupling, preferably a claw coupling. Reference character 18 has been applied to indicate the lower end of main operating shaft 11 which forms one half of a claw coupling and reference character 17 has been applied to indicate the upper end of auxiliary shaft 15 which forms the other half of a claw coupling cooperatively engaging the lower part of main coupling shaft 11 for transmittal of torques from the latter to auxiliary shaft 15. The aforementioned groove 20 is intended to receive an edge portion of a plate 22 having a central bore forming the edge portion of plate 22 to be received by groove 20. Thus plate 22 may be pivoted in clockwise as well as in counterclockwise direction about the central axis of the transfer switch structure which is the axis of cylindrical switch housing 1. Plate 22 is a support for the movable main current-carrying contacts 16 which are in the form of rollers cooperating with the fixed main current-carrying contacts 25. The lower end of auxiliary shaft 15 supports a driving disc 24 which may be keyed to auxiliary shaft 15, or otherwise secured to it in such a fashion as to be jointly pivotable with auxiliary shaft 15. Driving disc 24 and plate-shaped contact support 22 are coupled for joint motion by stud means 23 spaced from, and arranged parallel to, main shaft 11 and auxiliary shaft 15. j

The fixed current-carrying contacts 25 are conductively connected to the fixed main contacts 2 and are supported on the inner surface of switch housing 1. Reference numeral 21 has been applied to indicate brackets for securing movable current-carrying contacts 16 to contact support 22.

It is apparent from the foregoing that the structure which has been described and illustrated lends itself to use without and with current-carrying contacts 16, 25. If the current to be carried continuously is in the order of, say, 200 amps, contacts 16 and 25 may be dispensed with as well as all the parts required to operate the movable current-carrying contacts 16. Currents of a relatively low magnitude can safely be interrupted by means of arcing contacts of copper whose current-carrying capacity is high. If the currents to be interrupted and to be carried continuously are relatively large, say in the order of 400 amps, the main contacts and the auxiliary contacts must be made of a metal or alloy capable of withstanding arcing without showing any significant contact erosion. Such metals or alloys have a relatively limited current-carrying capacity and, therefore, the use of main contacts and of auxiliary contacts of relatively limited current-carrying capacity calls for the use of currentcarrying contacts. This may readily be achieved by adding to the structure of FIG. 2 a number of parts and thus converting it to the structure of FIG. 3.

The transfer switch which has been described above pertains to the class of transfer switches wherein the rotary motion of the main shaft 11 is converted by linkage means into radially inward and radially outward motions of the movable main contacts 3 and the movable auxiliary contacts 3' performed in a predetermined sequence, depending upon the particular circuitry of the transfer switch. The term linkage means is used in this context to include the sum total of the parts applied in any particular case for converting the rotary motion of the main shaft into radial motions of the contact support 30, and of the movable contacts 3, 3, respectively. In the instant structure the linkage means include shaft 31, linkages 8, shaft 32, contact operating plates 10 and helical springs 9. The same functions performed by the specific linkage means recited above might be performed by structurally more or less different linkage means.

It will be apparent from the foregiong to those skilled in the art that various changes and modifications may be made without departing from the spirit of the invention as set forth in the appended claims.

I claim as my invention:

1. A transfer switch for tap-chan ing regulating transformers comprising in combination:

(a) fixed main contacts and fixed auxiliary contacts arranged along a sector of a circle;

(b) movable main contacts cooperating with said fixed main contacts and movable auxiliary contacts cooperating with said fixed auxiliary contacts;

(0) linkage means for operating said movable main contacts and said movable auxiliary contacts radially inwardly and radially outwardly in a predetermined sequence;

(d) a main operating shaft arranged in the center of said sector of a circle for operating said linkage means;

(e) a substantially spider-shaped support for supporting said movable main contacts, said movable auxiliary contacts and said linkage means arranged at a level lower than said linkage means and including a bearing for the lower end of said main shaft;

(f) cooperating pairs of current-carrying contacts arranged below said spider-shaped support and including movable current-carrying contacts pivotally supported by said spider-shaped support;

(g) an auxiliary shaft for operating said movable current-carrying contacts separate from said main shaft and arranged in coaxial relation to said main shaft; and

(h) cooperating coupling means at juxtaposed ends of said main shaft and said auxiliary shaft engageable by axial movement of said auxiliary shaft relative to said main shaft in a direction longitudinally of said main shaft and of said auxiliary shaft.

2. A transfer switch as specified in claim 1 wherein said coupling means forms a claw coupling.

3. A transfer switch as specified in claim 1 wherein said spider-shaped support has an upper bore of relatively small diameter forming a bearing for said auxiliary shaft and a lower internally screw-threaded bore of relatively large diameter, an externally screw-threaded hub member being screwed into said lower bore and defining a circular groove, and a substantially plate-shaped contact support for said movable current-carrying contacts being pivotally guided in said circular groove.

4. A transfer switch as specified in claim 3 wherein a driving disc is secured to the lower end of said auxiliary shaft and wherein said driving disc and said substantially plate-shaped contact support are coupled for joint motion by stud means spaced from and parallel to said main shaft and said auxiliary shaft.

5. A transfer switch as specified in claim 4 including movable current-carrying contacts in the form of rollers, said rollers being conductively interconnected to form the neutral point of atransformer.

6. A transfer switch as specified in claim 5 including a cylindrical switch housing of insulating material supporting said fixed main contacts, said fixed auxiliary contacts and further supporting fixed current-carrying contacts cooperating With said movable current-carrying contacts.

6 References Cited UNITED STATES PATENTS 2,811,594 10/1957 Papouschek 20014 3,238,320 3/1966 Bleibtreu ZOO-11 ROBERT K. SCHAEFER, Primary Examiner. H. J. HOHAUSER, Assistant Examiner. 

1. A TRANSFER SWITCH FOR TAP-CHANGING REGULATING TRANSFORMERS COMPRISING IN COMBINATION: (A) FIXED MAIN CONTACTS AND FIXED AUXILIARY CONTACTS ARRANGED ALONG A SECTOR OF A CIRCLE; (B) MOVABLE MAIN CONTACTS COOPERATING WITH SAID FIXED MAIN CONTACTS AND MOVABLE AUXILIARY CONTACTS COOPERATING WITH SAID FIXED AUXILIARY CONTACTS; (C) LINKAGE MEANS FOR OPERATING SAID MOVABLE MAIN CONTACTS AND SAID MOVABLE AUXILIARY CONTACTS RADIALLY INWARDLY AND RADIALLY OUTWARDLY IN A PREDETERMINED SEQUENCE; (D) A MAIN OPERATING SHAFT ARRANGED IN THE CENTER OF SAID SECTOR OF A CIRCLE FOR OPERATING SAID LINKAGE MEANS; (E) A SUBSTANTIALLY SPIDER-SHAPED SUPPORT FOR SUPPORTING SAID MOVABLE MAIN CONTACTS, SAID MOVABLE AUXILIARY CONTACTS AND SAID LINKAGE MEANS ARRANGED AT A LEVEL LOWER THAN SAID LINKAGE MEANS AND INCLUDING A BEARING FOR THE LOWER END OF SAID MAIN SHAFT; (F) COOPERATING PAIRS OF CURRENT-CARRYING CONTACTS ARRANGED BELOW SAID SPIDER-SHAPED SUPPORT AND INCLUDING MOVABLE CURRENT-CARRYING CONTACTS PIVOTALLY SUPPORTED BY SAID SPIDER-SHAPED SUPPORT; (G) AN AUXILIARY SHAFT FOR OPERATING SAID MOVABLE CURRENT-CARRYING CONTACTS SEPARATE FROM SAID MAIN SHAFT AND ARRANGED IN COAXIAL RELATION TO SAID MAIN SHAFT; AND (H) COOPERATING COUPLING MEANS IN JUXTAPOSED ENDS OF SAID MAIN SHAFT AND SAID AUXILIARY SHAFT ENGEAGABLE BY AXIAL MOVEMENT OF SAID AUXILIARY SHAFT RELATIVE TO SAID MAIN SHAFT IN A DIRECTION LONGITUDINALLY OF SAID MAIN SHAFT AND OF SAID AUXILIARY SHAFT. 